Structures and energetics of hydrogen-terminated silicon nanowire surfaces

The analysis and density-functional tight-binding simulations of possible configurations of silicon nanowires (SiNWs) enclosed by low-index surfaces reveal a number of remarkable features. For wires along < 100 >, < 110 >, and < 111 > directions, many low-index facet configurations and cross sections are possible, making their controlled growth difficult. The < 112 > wires are the most attractive for research and applications because they have only one configuration of enclosing low-index facets with a rectangular cross section, enclosed with the most stable (111) facet and the (110) facet next to it. In general, the stability of the SiNWs is determined by a balance between (1) minimization of the surface energy gamma(111)<gamma(110)<gamma(001), and (2) minimization of the surface-to-volume ratio [svr; svr(hexagonal)>svr(rectangular)>svr(triangular)]. The energy band gaps follow the order of < 100 > wires>< 112 > wires>< 111 > wires>< 110 > wires. The results are compared with our recent scanning tunneling microscopy and transmission electron microscopy data. (c) 2005 American Institute of Physics.